Two animal models of aggressive behavior, namely hypothalamically elicited attack in cats, and shock-elicited aggression in rats are being investigated. The role which neurotransmitter systems and drugs which act on these systems is being determined. Stimulation of these systems uses electrical and chemical methods. Inhibition of the systems uses lesions either electrolytic or chemical, as well as chemical metabolic inhibitors. The interrelationship with important environmental parameters such as noise is also being investigated.